PROJECT SUMMARY Congenital heart disease patients with functional single ventricle (FSV) anatomy ultimately require a Fontan operation for long term survival. The goal of the Fontan operation is to re-route systemic venous blood to the pulmonary circulation without passing through an intervening ventricular chamber. As a result, blood flow to the lungs is almost entirely a passive, non-pulsatile process. Although morbidity and mortality associated with the Fontan procedure has improved considerably over the last decade, there are still many patients who develop complications and eventual Fontan failure for reasons we do not yet entirely understand. The pressure in the Fontan pathway is arguably the single measurement that most closely predicts the overall health of the palliated circulation. This measurement reflects the general condition of all the cardiac and vascular structures that lie between the branch pulmonary arteries and the systemic single ventricle. Unfortunately, Fontan pressure measurements obtained in the catheterization laboratory are variably, and often erroneously, influenced by elements involved in performing the procedure itself. The unique physiology of the Fontan allows these factors to have a more significant influence on the pressure measurements compared to patients with biventricular anatomy and physiology. Furthermore, the invasive cath lab measurement provides only a snapshot of what is occurring within the unique circulation and does not represent what is taking place during normal activities of daily living. The ability to measure chronic, serial Fontan pathway pressures in an ambulatory setting will result in a better understanding of the Fontan physiology and should ultimately improve morbidity and mortality associated with this high risk patient population. Investigators on this grant have been developing a novel miniature wireless implantable pressure sensor to measure the pressure in the Fontan pathway of patients with single ventricle anatomy. Commercial development of such a device would represent a significant technological advancement in providing care to this high risk patient population. In the proposed grant, investigators at the University of Michigan (UM) will lead the effort to carry out the Investigational Device Exemption (IDE) study that is required before the device can be approved for marketing and sales in the United States. The industry sponsor, Integrated Sensing Systems, Inc. (ISSYS) will provide the investigational device and equipment required for each clinical site to carry-out the study. Investigators at UM will design the multi-center IDE trial, serve as the Sponsor Investigator for the IDE trial, enroll patients at the UM, oversee enrollment of patients at the other clinical trial sites, and work with FDA and ISSYS to submit the final application for Humanitarian Device Exemption (HDE) once the trial and follow-up is completed. ISSYS will be responsible for performing all the post HDE activities, including Post Market Vigilance, will finalize the manufacturing process for production of these implants, maintain the FDA-required medical-device quality infrastructure, and be in charge of all commercialization activities.